1. Field of the Invention
The present invention relates to a disk cartridge for use in a disk-shaped recording medium, which intends to make the disk cartridge even more compact.
2. Description of the Related Art
An optical disk is an example of the disk-shaped recording medium. In many cases, the optical disk is used, being contained inside a disk cartridge to prevent a recording surface of the disk from being contaminated with grease or dirt on fingers and to enhance ease of handling. To ensure that the optical disk can be properly contained in the disk cartridge, therefore, the width of the disk cartridge is made larger than the outside diameter of the disk in conventional disk cartridges. Japanese Patent Laid-open No. Hei 10-269740 discloses an example of the disk cartridge of this type.
The prior art commonly found in conventional disk cartridges will be explained with reference to FIGS. 9 through 11. FIG. 9 is a perspective view of a conventional disk cartridge 101. FIG. 10 is a view showing the disk cartridge in relation to a disk housed in the disk cartridge. FIG. 11 is an exploded view of the disk cartridge 101. The disk cartridge 101 includes two cases or a case 102a and a case 102b, which are larger than the outside diameter of a disk 105, a shutter 103, a shutter spring 104, and a write-protect block 109. Each of the case 102a and the case 102b is shaped so as to form a disk space 111 in which the disk can be contained, when the cases 102a and 102b are mated with each other. In addition, a disk movement restricting portion 112 that restricts the movement of the disk 105 in the direction parallel with a disk surface on an outer periphery of the disk space 111. The fact that the disk 105 is located within the disk space 111 allows the disk 105 to be rotated without coming into contact with the case 102a or case 102b. Furthermore, the case 102a is mated with the case 102b so as to house the disk 105 therebetween. This allows a major part of the entire disk 105 to be isolated from the outside of the cartridge.
An opening window 110a and an opening window 110b are provided in the case 102a and the case 102b, respectively. The shutter 103 is used to open or close these opening windows 110a, 110b. In recording and reproducing apparatus, an optical head accesses the disk 105 through these opening windows 110a, 110b to record or reproduce information on the disk. The shutter spring 104 urges the shutter 103 in a direction to close the opening windows 110a, 110b at all times. It is designed to close the opening windows 110a, 110b whenever the disk cartridge 101 is located outside the recording and reproducing apparatus. As is known from the foregoing description, the cases 102a, 102b and the shutter 103 are designed to isolate the disk 105 from the outside when the disk is outside the recording and reproducing apparatus. The write-protect block 109 is a switch that selects either to enable or disable recording the disk 105. The user himself or herself actually operates the switch to prevent information recorded on the disk from being inadvertently erased.
The conventional disk cartridge is configured such that its width is wider than the outside diameter of the disk. It should be ensured that the disk 105 rotates in the disk space 111 inside the disk cartridge 101 without coming into contact with any part thereof. To make sure of that, it is necessary to take into consideration radial runout or the like that occurs when an eccentric disk rotates as well as the outside diameter of the disk 105, when disposing the disk movement restricting portion 112 provided on the outer periphery of the disk space 111. As shown in FIG. 10, therefore, the following relationship holds true between a width W2 of the disk cartridge 101 and an outside diameter D2 of the disk 105:W2>D2.
In addition, side walls should be provided along edges of the disk space 111 in order to isolate the disk 105 from the outside completely. It is possible to let the disk movement restricting portion 112 function also as the side walls. Referring to FIG. 11, if the shortest distance between a rotation axis of the disk 105 and the disk movement restricting portion 112 is R2, the following relationship holds true between the width W2 of the disk cartridge 101 and the distance R2 between the rotation axis and the disk space edge, since the thickness of the disk movement restricting portion 112 is added to the width of the disk cartridge 101:W2>2×R2.
To use the disk cartridge, therefore, the cartridge must be larger than the disk. If the disk cartridge is larger than the disk, it becomes difficult to make a disk apparatus that uses the disk cartridge more compact.